This microcomputer (PDP-11/03) data system supervises the acquisition and processing of information from an analytical ultracentrifuge and a circular dichroic spectropolarimeter used in MDB, NHLBI to investigate the interactions between human lipoprotein subunits. Current capabilities include acquisition, display, and preprocessing of data from the ultracentrifuge and transfer of preprocessed data files to the DECsystem-10 for further analysis. The nonlinear analyses necessary for the characterization of interacting systems are then carried out under MLAB on the DECsystem-10. CLINK, the PDP-11/PDP-10 communications software package jointly developed by CSL and CCB, is used to perform the data transfers. Computation of molecular weights for both associating and non-associating systems can be performed under MLAB using predefined procedures invoked by a few simple commands. An interface has been constructed to acquire the spectropolarimeter signals, ellipticity, and wavelength. Software support includes the ability to add, subtract, and average CD spectra and to transfer files to the PDP-10 for further analysis.